Gas metal arc welding is used widely because this is the high efficient and quality joining technology. However, the welding defect occurs because of the arc deflection caused by the strong wind. The preventive technology of arc deflection is important. It is possible that the arc deflection is prevented using Lorentz force caused by the transverse magnetic field against lateral gas. The arc deflection has not been elucidated because the measurement of three-dimensionally asymmetric temperature and the axial flow velocity distribution of arc is difficult at the only experiment. The 3-D numerical analysis is necessary to elucidate flow velocity affected by Lorentz force. In this study, the flow velocity distribution in the arc affected by the transverse magnetic field with the lateral gas flow for the elucidation of arc deflection was analyzed. The arc deflection was calculated with lateral gas flow and changing the transverse magnetic flux density using the electromagnetic thermal fluid (EMTF) simulation. As a result, the difference in arc deflection distance from the experiment was 0.4mm with a transverse magnetic flux density, indicating a similar tendency. In addition, the axial flow velocity increased and the radial flow velocity decreased with the electromagnetic force in the opposite direction against crosswind. Along with this, the arc deflection distance decreased.